Audio spectrum analyzer and method of arranging resonators included therein

ABSTRACT

A spectrum analyzer includes: a support substrate; and a plurality of resonators that have center frequencies different from each other, one end of each of the plurality of resonators being fixed to the support substrate. The plurality of resonators are arranged so that an interval between resonators having adjacent center frequencies is secured by a certain value or greater, thus reducing coupling and increasing analysis accuracy.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from Korean Patent Application No.10-2016-0099059, filed on Aug. 3, 2016 in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein byreference in its entirety.

BACKGROUND 1. Field

Exemplary embodiments relate to audio spectrum analyzers and methods ofarranging resonators included therein.

2. Description of the Related Art

Spectrum analyzers, which analyze audio or vibration spectrums, may beused for situation recognition, speech recognition, speaker recognition,or the like in cellphones, computers, home appliances, vehicles, orsmart home environments, or may be mounted on home appliances, vehicles,buildings, or the like to analyze vibration information.

Generally, frequency domain information of an audio signal is acquiredin such a way that an audio signal input to a microphone having widebandcharacteristics passes through an analog-to-digital converter (ADC) andthen Fourier-transformed. Such a frequency information acquisitionmethod imposes a heavy burden in terms of the amount of computationrequired for Fourier transformation and has a trade-off relationshipbetween frequency resolution and time resolution. Thus, it may bedifficult to improve resolutions of both time information and frequencyinformation.

SUMMARY

Exemplary embodiments address at least the above problems and/ordisadvantages and other disadvantages not described above. Also, theexemplary embodiments are not required to overcome the disadvantagesdescribed above, and may not overcome any of the problems describedabove.

One or more exemplary embodiments audio spectrum analyzers with improvedresolution.

Further, one or more exemplary embodiments methods of arrangingresonators, capable of reducing coupling between resonators havingdifferent center frequencies.

According to an aspect of an exemplary embodiment, there is provided aspectrum analyzer including: a support substrate; and a plurality ofresonators that have center frequencies different from each other, oneend of each of the plurality of resonators being fixed to the supportsubstrate.

Each of the plurality of resonators may include: a fixing portion fixedto the support substrate; a movable portion movable in response to anaudio signal; and a sensor configured to sense a movement of the movableportion.

The support substrate may include a through-hole, and the movableportion of each of the plurality of resonators faces the through-hole.

The plurality of resonators may be arranged in a flat formation withoutoverlapping one another.

The fixing portions of the plurality of resonators may be arranged tohave a trajectory along a cross-sectional shape of the through-hole.

A cross-sectional shape of the through-hole may be a rectangular shape,and the fixing portions of the plurality of resonators may be arrangedto have a trajectory along two parallel sides of the rectangular shape.

A separation distance between two resonators having center frequenciesimmediately adjacent to each other, among the plurality of resonators,may be greater than a shortest separation distance among separationdistances between the plurality of resonators.

A center frequency difference between two resonators spatiallyimmediately adjacent to each other, among the plurality of resonators,may be greater than a smallest center frequency difference among centerfrequency differences between the plurality of resonators.

When N denotes a number of the plurality of resonators, R_(k) denotesthe plurality of resonators in order of center frequencies, k denotes anatural number from 1 to N, m is any one of aliquots of N other than 1and N, and j is a natural number from 1 to m, the plurality ofresonators are grouped into m subgroups SG_j. When j is different fromm, each of the subgroups SG_j includes resonators R_(k) satisfying (kmod m)=j. When j is equal to m, each of the subgroups SG_j includesresonators R_(k) satisfying (k mod m)=0, and resonators R_(k) belongingto a same subgroup SG_j are arranged adjacent to each other in order ofthe center frequencies.

The subgroups SG_j may be arranged in order of the j values.

m may be one medium value or two median values of the aliquots of N.

m may be a natural number greater than 2, and the fixing portions of theplurality of resonators may be arranged to have a trajectory in apolygonal shape, a circular shape, or a closed curve shape.

The fixing portions of the plurality of resonators may are arranged tohave a trajectory in an m-polygonal shape with m sides.

m may be an even number, and he fixing portions of the plurality ofresonators may be arranged to have a trajectory in a shape of twostraight lines parallel to each other.

The fixing portions of the resonators belonging to subgroups SG_1 toSG_m/2 among the subgroups SG_j are arranged to have a trajectory in ashape of a first straight line, and the fixing portions of theresonators belonging to subgroups SG_(m/2)+1 to SG_m among the subgroupsSG_j are arranged to have a trajectory in a shape of a second straightline parallel to the first straight line.

Resonators in a first subgroup of the plurality of resonators andresonators in a second subgroup of the plurality resonators may faceeach other and may be arranged in reverse order of the centerfrequencies.

When the center frequencies of the plurality of resonators are within arange between a first frequency F1 and a second frequency F2, the centerfrequencies of the plurality of resonators may be F1+(k−1)(F2−F1)/(N−1),respectively. Here, N is a number of the plurality of resonators, and kis a natural number from 1 to N.

The center frequencies of the plurality of resonators may be set atequal-ratio intervals.

According to an aspect of another exemplary embodiment, there isprovided a method of arranging resonators of a spectrum analyzerincluding: setting a frequency range of frequency f a number N of aplurality of resonators R_(k), when k is a natural number from 1 to N;setting center frequencies of the plurality of resonators R_(k) to bedifferent values within the set frequency range; setting an arrangementperiod p of the plurality of resonators R_(k); and arranging theplurality of resonators R_(k) so that a pitch between two resonators ofthe plurality of resonators R_(k), which have the center frequenciesimmediately adjacent to each other, is 2p or greater.

The frequency range may be set to be between F1 and F2, the centerfrequencies of the plurality of resonators R_(k) may be set to beF1+(k−1)(F2−F1)/(N−1), and the plurality of resonators may be arrangedso that a center frequency difference between two resonators of theplurality of resonators R_(k), which are spatially immediately adjacentto each other, is 2(F2−F1)/N or greater.

The center frequencies of the plurality of resonators R_(k) may be setat equal-ratio intervals r, and the plurality of resonators R_(k) arearranged so that a center frequency ratio between two resonators of theplurality of resonators (R_(k)), which are spatially immediatelyadjacent to each other, is 2r or greater.

The plurality of resonators R_(k) may be grouped into m subgroups SG_jwhen j is a natural number from 1 to m, and m is any one of aliquots ofN other than 1 and N. When j is different from m, each of the subgroupsSG_j may include resonators R_(k) satisfying (k mod m)=j. When j isequal to m, each of the subgroups SG_j may include resonators R_(k)satisfying (k mod m)=0. Resonators R_(k) belonging to a same subgroupSG_j may be arranged adjacent to each other in order of the centerfrequencies.

According to an aspect of another exemplary embodiment, there isprovided a spectrum analyzer including: a support substrate including athrough-hole; and a plurality of resonators. Each of the plurality ofresonators has a first end that is fixed to the support substrate and asecond end that extends from the first end toward the through-hole to beapart from the support substrate. The plurality of resonators areclassified into m number of groups, wherein m is a natural number.Resonators in a same group among the m number of groups are disposed tobe adjacent to each other. A difference between a central frequency of afirst resonator in one group and a central frequency of a secondresonator in the one group is a multiplication of m and Δf, wherein theΔf is F divided by N when F is a frequency range in which each of theplurality of resonators operates and N is a number of the plurality ofresonators.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or other aspects will be more apparent by describingcertain exemplary embodiments, with reference to the accompanyingdrawings, in which:

FIG. 1 is a perspective view illustrating a schematic configuration of aspectrum analyzer according to an exemplary embodiment;

FIGS. 2A and 2B are cross-sectional views illustrating a configurationof one resonator from among a plurality of resonators included in thespectrum analyzer of FIG. 1.

FIG. 2C is a graph showing frequency response characteristics of the oneresonator;

FIG. 3 is a conceptual diagram of an analysis of a frequency componentof an audio signal performed by using the spectrum analyzer of FIG. 1;

FIG. 4 is a graph showing a frequency resolution and a time resolutionimplemented by the spectrum analyzer of FIG. 1, when compared to thecase of using a Fourier transform method;

FIG. 5 conceptually illustrates a change of a coupling effect accordingto a center frequency difference between resonators arranged spatiallyadjacent to each other;

FIG. 6 conceptually illustrates a change of a coupling effect accordingto a separation distance between resonators, whose center frequenciesare adjacent to each other;

FIGS. 7 and 8 are flowcharts of a method of arranging resonators,according to an embodiment;

FIGS. 9A, 9B, 9C, 9D, and 9E illustrate resonator arrangement exampleswhen the number of resonators is 12 and the number of subgroups is 1, 2,3, 4, and 6, respectively;

FIG. 10 illustrates an example in which a plurality of resonators aredivided into m subgroups that are arranged in a circular shape;

FIG. 11 illustrates an example in which resonators are arranged in orderof center frequencies in each subgroup of FIG. 10;

FIG. 12 is a perspective view illustrating a schematic configuration ofa spectrum analyzer according to another exemplary embodiment;

FIG. 13 is a graph showing frequency response characteristics due tothree resonators arranged spatially adjacent to one another in thespectrum analyzer of FIG. 12;

FIG. 14 is a graph showing frequency response characteristics due tothree resonators, whose center frequencies are adjacent to one another,in the spectrum analyzer of FIG. 12;

FIG. 15 illustrates an example in which a plurality of resonators aredivided into m subgroups arranged in a rectangular shape in a spectrumanalyzer according to another exemplary embodiment;

FIG. 16 illustrates an example in which resonators are arranged in orderof center frequencies in each subgroup of FIG. 15;

FIG. 17 illustrates an example in which resonators of subgroups facingeach other are arranged in reverse order of center frequencies;

FIG. 18 is a perspective view illustrating a schematic configuration ofa spectrum analyzer according to another exemplary embodiment;

FIG. 19 is a graph showing frequency response characteristics due tothree resonators arranged spatially adjacent to one another in thespectrum analyzer of FIG. 18;

FIG. 20 is a graph showing frequency response characteristics due to tworesonators whose center frequencies are adjacent to each other, in thespectrum analyzer of FIG. 18;

FIG. 21 is a plan view illustrating an example of a resonatorarrangement in a spectrum analyzer according to another exemplaryembodiment;

FIG. 22 is a plan view illustrating an example of a resonatorarrangement in a spectrum analyzer according to another exemplaryembodiment; and

FIGS. 23A, 23B, and 23C are graphs showing examples of methods ofsetting center frequencies of resonators used in spectrum analyzersaccording to exemplary embodiments.

DETAILED DESCRIPTION

Exemplary embodiments are described in greater detail below withreference to the accompanying drawings.

In the following description, like drawing reference numerals are usedfor like elements, even in different drawings. The matters defined inthe description, such as detailed construction and elements, areprovided to assist in a comprehensive understanding of the exemplaryembodiments. However, it is apparent that the exemplary embodiments canbe practiced without those specifically defined matters. Also,well-known functions or constructions are not described in detail sincethey would obscure the description with unnecessary detail. It will beunderstood that when a layer, region, or component is referred to asbeing “formed on,” another layer, region, or component, it can bedirectly or indirectly formed on the other layer, region, or component.

As used herein, the singular forms “a,” “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising” used herein specify the presence of stated featuresor components, but do not preclude the presence or addition of one ormore other features or components.

As used herein, the term “the” or similar indicative terms correspond toboth the singular form and the plural form.

Operations constituting a method may be performed in an appropriateorder, unless operations clearly indicate otherwise. The method is notlimited to the order of operations described herein. The use of any andall examples, or exemplary language (e.g., “such as”) provided herein,is intended merely to better illuminate the underlying concept and doesnot pose a limitation on the scope of the disclosure.

FIG. 1 is a perspective view illustrating a schematic configuration of aspectrum analyzer 100 according to an exemplary embodiment. FIGS. 2A and2B are cross-sectional views illustrating a configuration of oneresonator R from among a plurality of resonators included in thespectrum analyzer 100 of FIG. 1, and FIG. 2C is a graph showingfrequency response characteristics of the one resonator R.

Referring to FIG. 1, the spectrum analyzer 100 includes a supportsubstrate 110 and a resonator array 120. The resonator array 120includes a plurality of resonators R, one end of each of which is fixedto the support substrate 110, and center frequencies of the resonators Rare different from one another.

As illustrated in FIGS. 2A and 2B, the resonator R includes a fixingportion 10 fixed to the support substrate 110, a movable portion 30movable in response to a signal, and a sensor 20 configured to sense amovement of the movable portion 30. The resonator R may further includea mass body 40 configured to provide a certain mass m to the movableportion 30.

A through-hole TH may be formed in the support substrate 110, and theplurality of resonators R may be arranged so that the movable portion 30of each of the plurality of resonators R faces the through-hole TH. Thethrough-hole TH provides a space where the movable portion 30 isvibrated by an external force, and there is no particular limitation toa shape or size thereof as long as the through-hole TH satisfies thiscondition. The support substrate 110 may include various materials, suchas silicon or the like.

The plurality of resonators R may be arranged in a flat form withoutoverlapping one another. That is, the plurality of resonators R may bearranged to be simultaneously exposed to a physical signal input path asa whole. An arrangement trajectory of the fixing portions 10 of theplurality of resonators R may be along a cross-sectional shape of thethrough-hole TH. The through-hole TH is illustrated as having a circularshape, but embodiments are not limited thereto. The through-hole TH mayhave a polygonal shape or various closed curve shapes.

The movable portion 30 may include an elastic film. The elastic film mayhave a length of L and a width of W, which are factors to determineresonance characteristics of the resonator R together with the mass m ofthe mass body 40. The elastic film may include a silicone, a metal, or apolymer.

The sensor 20 may include a sensor layer configured to sense themovement of the movable portion 30. The sensor 20 may include, forexample, a piezoelectric element. In this case, the sensor 20 may have astructure in which an electrode layer, a piezoelectric material layer,and an electrode layer are stacked. ZnO, SnO, PZT, ZnSnO₃,polyvinylidene fluoride (PVDF), poly(vinylidenefluoride-trifluoroethylene) (P(VDF-TrFE)), AlN, or PMN-PT may be used asthe piezoelectric material. A metal material or various conductivematerials may be used to form the electrode layer.

The resonators R may have a width of several micrometers or less, athickness of several micrometers or less, and a length of severalmillimeters or less. The resonators R having ultra-small sizes may bemanufactured by a microelectromechanical system (MEMS) process.

The resonator R vertically vibrates along a Z direction in response toan external signal, and a displacement value z is determined accordingto the following motion equation:

${{m\frac{d^{2}z}{{dt}^{2}}} + {c\frac{dz}{dt}} + {kz}} = {F_{0}\cos \; \omega \; t}$

Here, c is a damping coefficient, k is the modulus of elasticity, and F₀cos ωt is a driving force and indicates an action caused by a signalinput to the resonator R. The value of k is determined by a physicalproperty and a shape of the movable portion 30.

Due to the motion equation, the resonator R shows frequency responsecharacteristics having a center frequency f₀ and a bandwidth BW, asillustrated in FIG. 2C.

The center frequency f₀ is as follows:

$f_{0} = {\frac{1}{2\pi}\sqrt{\frac{k}{m}}}$

The bandwidth BW means a frequency bandwidth representing half of afrequency response value (z-magnitude) at the center frequency f₀.

The resonators R included in the spectrum analyzer 100 are designed tohave different center frequencies and may sense a frequency of a certainband with respect to the center frequency f₀.

FIG. 3 is a conceptual diagram of an analysis of a frequency componentof an audio signal performed by using the spectrum analyzer 100 of FIG.1.

When an audio signal Wi having various frequency components is input tothe spectrum analyzer 100, each of the resonators R vibrates in responseto a sensing frequency band of each of the resonators R among thefrequency components included in the audio signal Wi. The centerfrequencies of the resonators R may be set so that the resonators Rreceive an audio signal having an audible frequency band of about 20 Hzto about 20 kHz, an ultrasonic band of about 20 kHz or greater, or aninfrasound band of about 20 kHz or less.

Since the resonators R are vibrated by the input audio signal and theresonators R are vibrated in response to different audio frequencybands, the resonators R may sense different frequency bands.

For example, as illustrated in FIG. 3, the resonators, whichrespectively have center frequencies f₁, f₂, and f₃, output signalsresponsive to the corresponding frequency components. That is, since theoutputs of the resonators carry corresponding frequency information, afrequency resolution is independently determined by the number ofresonators. A time resolution may be equal to or in direction proportionto an instant output speed from each of the resonators.

FIG. 4 is a graph showing a frequency resolution and a time resolutionimplemented by the spectrum analyzer 100 of FIG. 1, when compared to thecase of using a Fourier transform method.

According to a short-time Fourier transform (STFT) method, an inputsignal is divided into constant time intervals, i.e., frames, and fastFourier transformation (TFT) is performed on each frame, so as toobserve a change in frequency distribution according to time. If theframe is finely divided, a change according to time can be easilyobserved, but information inside the frame is reduced. Thus, frequencyinformation becomes insufficient. If the frame is widely divided,frequency information becomes clear, but a temporal change becomesinsensitive. This is called Gabor uncertainty or Fourier uncertainty. ΔTand ΔF are limited to values on a dashed line indicated in the graph. Inthe present exemplary embodiment, the frequency resolution and the timeresolution may be independently secured without such limitations and canbe selectively designed with any values within a hatched region.

In the spectrum analyzer 100 of FIG. 1, the plurality of resonators Rare arranged according to the magnitude of the center frequencies, butexemplary embodiments are not limited thereto. The plurality ofresonators R may be arranged in other arrangement methods capable ofimproving output characteristics.

As illustrated in FIG. 2C, the frequency response graph of the resonatorR has a certain bandwidth BW. Thus, a Q value defined as f₀/BW isfinite. As the Q value increases, the frequency response characteristicsbecome more sensitive. As the Q value decreases, the resonator alsoresponds to a frequency of an adjacent band, as well as the centerfrequency. Since the plurality of resonators R are integrated within alimited space, coupling occurs between the resonators R. Since thecoupling effect is related to both a spatial distance between theresonators R and a center frequency difference between the adjacentresonators R, it may be necessary to take these factors into account soas to reduce the coupling.

FIG. 5 conceptually illustrates a change of the coupling effectaccording to the center frequency difference between the resonatorsarranged spatially adjacent to each other.

Specifically, FIG. 5 shows frequency response characteristics due to tworesonators in three cases in which a spatial separation distance is dand center frequency differences are (Δf)₁, (Δf)₂, and (Δf)₃.

Referring to FIG. 5, as the center frequency difference becomes smaller,stronger coupling occurs. When the center frequency difference is (Δf)₁,the resonator having a center frequency of f_(i) also exhibits a peak inresponse to a frequency of f_(i−1), and the resonator having a centerfrequency of f_(i+1) also exhibits a peak in response to the frequencyof f_(i).

When the center frequency difference increases to (Δf)₂, the resonatorhaving the center frequency of f_(i) does not exhibit a peak in responseto the frequency of f_(i+1), but the resonator having the centerfrequency of f_(i+1) exhibits a peak in response to the frequency off_(i).

When the center frequency difference further increases to (Δ)₃, theresonator having the center frequency of f_(i) does not exhibit a peakin response to the frequency of f_(i+1), and the resonator having thecenter frequency of f_(i+1) does not exhibit a peak in response to thefrequency of f_(i). That is, coupling between the two resonators doesnot occur.

From these analyses, it can be seen that coupling can be reduced in sucha way that the center frequency difference between the resonatorsarranged spatially adjacent to each other is set to be a certain valueor greater, for example, the center frequency difference therebetween isset to be greater than a bandwidth of each of the resonators.

FIG. 6 conceptually illustrates a change of the coupling effectaccording to the separation distance between resonators, whose thecenter frequencies are adjacent to each other.

Specifically, FIG. 6 shows frequency response characteristics due to tworesonators in three cases in which a separation distance between tworesonators having a center frequency difference of Δf increases to d₁,d₂, and d₃.

Referring to FIG. 6, as the separation distance between the resonatorsbecomes shorter, greater coupling occurs. When the separation distancebetween the two resonators is d₁, the resonator having a centerfrequency of f_(i) also exhibits a peak in response to a frequency off_(i+1), and the resonator having a center frequency of f_(i+1) alsoexhibits a peak in response to the frequency of f_(i).

In a case where the separation distance between the two resonatorsincreases to d₂, a magnitude of a peak obtained when the resonatorhaving the center frequency of f_(i) responds to the frequency off_(i+1) and a magnitude of a peak obtained when the resonator having thecenter frequency of f_(i+1) responds to the frequency of f_(i) aresmaller than those in a case where the separation distance between thetwo resonators is d₁.

In a case where the center frequency difference further increases to d₃,the resonator having the center frequency of f_(i) does not exhibit apeak in response to the frequency of f_(i+1), and the resonator havingthe center frequency of f_(i+1) does not exhibit a peak in response tothe frequency of f_(i). That is, coupling between the two resonatorsdoes not occur.

From these analyses, it can be seen that coupling can be reduced in sucha way that the spatial separation distance between the resonators havinga small center frequency difference is set to be a certain value orgreater.

By taking this into account, the arrangement of the resonators R of theresonator array 120 in the spectrum analyzer 100 of FIG. 1 may bemodified to reduce coupling.

For example, the plurality of resonators R may be arranged so that theseparation distance between two resonators R having center frequenciesimmediately adjacent to each other is greater than the shortestseparation distance among the separation distances between the pluralityof resonators R.

Alternatively, the plurality of resonators R may be arranged so that theseparation distance between two resonators R having center frequenciesimmediately adjacent to each other is greater than a predeterminedvalue.

Alternatively, the plurality of resonators R may be arranged so that thecenter frequency difference between two resonators R spatiallyimmediately adjacent to each other is greater than the smallest centerfrequency difference among the center frequency differences between theplurality of resonators R.

FIGS. 7 and 8 are flowcharts of a method of arranging resonators of aspectrum analyzer, according to an exemplary embodiment.

Referring to FIG. 7, a frequency (f) range F1≦f≦F2 and a number N of aplurality of resonators R_(k) (where k is a natural number from 1 to N)are set for analysis (operation S100).

Center frequencies of the plurality of resonators and an arrangementperiod p of the plurality of resonators R_(k) are set (operation S200).The arrangement period p is a distance between centers of adjacentresonators and is a value corresponding to d+w when the separationdistance is d. The distance between the centers of the resonators(R_(k)) may be also referred to as a pitch. The center frequencies ofthe plurality of resonators R_(k) are set to be different values withinthe set frequency range F1≦f≦F2. The index k naming the plurality ofresonators R_(k) may be determined in descending order of the centerfrequencies. The rule for setting the center frequencies may bevariously determined. For example, the center frequencies may be set atequal-difference intervals or equal-ratio intervals. Alternatively, thecenter frequencies may be at arbitrary intervals. For example, thecenter frequencies may be set densely in a specific frequency sectionand may be set sparsely in the other frequency sections.

The plurality of resonators R_(k), whose center frequencies aredesigned, are arranged in a particular manner. In order to preventoccurrence of coupling, the plurality of resonators R_(k) are arrangedso that a distance between centers of resonators R_(k), of which thecenter frequencies are immediately adjacent to each other, is 2p orgreater (operation S300).

Alternatively or additionally, the plurality of resonators R_(k) may bearranged so that a center frequency difference between the resonatorsR_(k) spatially immediately adjacent to each other is a certain value orgreater.

For example, when the center frequencies of the plurality of resonatorsR_(k) are set at equal-difference intervals, that is, when the centerfrequencies of the plurality of resonators R_(k) are respectivelyF1+(k−1)(F2−F1)/(N−1) (where k is a natural number from 1 to N), theplurality of resonators R_(k) may be arranged so that the centerfrequency difference between the resonators R_(k) spatially immediatelyadjacent to each other is 2(F2−F1)/N or greater.

Alternatively, when the center frequencies of the plurality ofresonators R_(k) are set at equal-ratio (r) intervals, that is, ratio ofcenter frequencies of the two resonators having center frequenciesimmediately adjacent to each other, among of the plurality of resonatorsR_(k), are set to have a constant value r, the plurality of resonatorsR_(k) may be arranged so that a center frequency ratio between theresonators R_(k) spatially adjacent to each other is 2r or greater.

As described above with reference to FIGS. 5 and 6, such arrangements ofthe resonators R_(k) are done for increasing the interval between theresonators R_(k), of which the center frequencies are immediatelyadjacent to each other, as much as possible and/or increasing the centerfrequency difference between the resonators R_(k) spatially immediatelyadjacent to each other. That is, the optimal combination of the tworequirements or the resonator arrangement focusing on either of the tworequirements may be selectively used.

A method of grouping the plurality of resonators R_(k) into subgroupswill be described with reference to FIG. 8.

The plurality of resonators R_(k) may be grouped into m subgroups SG_j(where j is a natural number from 1 to m) (operation S310). Inparticular, the plurality of resonators R_(k) may be grouped based onthe modulus of m.

The subgroups SG_j may be defined by a remainder obtained when kindicating the center frequency order of the resonators R_(k) is dividedby the number m of subgroups. That is, SG_j (j≠m) includes resonatorsR_(k) satisfying (k mod m)=j, and SG_j (j=m) includes resonators R_(k)satisfying (k mod m)=0.

The number m of subgroups may be aliquots of N, and may be any one ofthe aliquots of N other than 1 and N. When m is the aliquot of N, thesame number of resonators may be included in each subgroup. However, mis not necessarily limited to the aliquot of N.

The resonators R_(k) belonging to the same subgroup SG_j are arrangedadjacent to each other in order of the center frequencies (operationS320). Also, the subgroups SG_j may be arranged in order of the index jdefining the subgroups (operation S330).

FIGS. 9A to 9E illustrate resonator arrangement examples when the numberof resonators is 12 and the number of subgroups is 1, 2, 3, 4, and 6,respectively.

FIG. 9A illustrates an example in which the number of subgroups is 1,that is, a plurality of resonators are arranged in order of centerfrequencies without being grouped. In this arrangement, a centerfrequency difference between the resonators spatially adjacent to eachother is smallest. That is, the resonators have a constant arrangementperiod p, and a center frequency spacing between the adjacent resonatorsis Δt

Δf may be differently defined according to a method of setting thecenter frequencies of the resonators. For example, when the centerfrequencies are set at equal-difference intervals, Δf is defined as(F2−F1)/N. When the center frequencies are set at equal-ratio (r)intervals, Δf is defined as r.

FIG. 9B illustrates a case where two subgroups SG_1 and SG_2 are formed.The subgroup SG_1 includes resonators R_(k) (k=1, 3, 5, 7, 9, 11) andthe subgroup SG_2 includes resonators R_(k) (k=2, 4, 6, 8, 10, 12). Theresonators R_(k) in the subgroups SG_1 and SG_2 are arranged in order ofthe center frequencies. In this case, a frequency distance between theresonators R₁ and R₃ spatially immediately adjacent to each other is2Δf, and a spatial distance between the resonators R₁ and R₂, of whichthe center frequencies are immediately adjacent to each other, is 6p.

FIG. 9C illustrates a case where three subgroups SG_1, SG_2, and SG_3are formed. The subgroup SG_1 includes resonators R_(k) (k=1, 4, 7, 10),the subgroup SG_2 includes resonators R_(k) (k=2, 5, 8, 11), and thesubgroup SG_3 includes resonators R_(k) (k=3, 6, 9, 12). The resonatorsR_(k) in the subgroups SG_1, SG_2, and SG_3 are arranged in order of thecenter frequencies. In this case, a frequency distance between theresonators R₁ and R₄ spatially immediately adjacent to each other is3Δf, and a spatial distance between the resonators R₁ and R₂, of whichthe center frequencies are immediately adjacent to each other, is 4p.

FIG. 9D illustrates a case where four subgroups SG_1, SG_2, SG_3, andSG_4 are formed. The subgroup SG_1 includes resonators R_(k) (k=1, 5,9), the subgroup SG_2 includes resonators R_(k) (k=2, 6, 10), thesubgroup SG_3 includes resonators R_(k) (k=3, 7, 11), and the subgroupSG_4 includes resonators R_(k) (k=4, 8, 12). The resonators R_(k) in thesubgroups SG_1, SG_2, SG_3, and SG_4 are arranged in order of the centerfrequencies. In this case, a frequency distance between the resonatorsR₁ and R₅ spatially immediately adjacent to each other is 4Δf, and aspatial distance between the resonators R₁ and R₂, of which the centerfrequencies are immediately adjacent to each other, is 3p.

FIG. 9E illustrates a case where six subgroups are formed. In this case,a frequency distance between the resonators R₁ and R₇ spatiallyimmediately adjacent to each other is 6Δf, and a spatial distancebetween the resonators R₁ and R₂, of which the center frequencies areimmediately adjacent to each other, is 2p.

As described above, the number of subgroups may be variously selectedthrough an appropriate combination of aspects of securing the distancebetween the resonators, of which the center frequencies are adjacent toeach other, or securing the center frequency difference between theresonators spatially adjacent to each other. The case of FIG. 9B furtherfocuses on the aspect of securing the distance between the resonators,of which the center frequencies are adjacent to each other, and the caseof FIG. 9E further focuses on the aspect of securing the centerfrequency difference between the resonators spatially adjacent to eachother.

In order to appropriately combine the two aspects, the number m ofsubgroups may be determined to be a median value when the aliquots of Nare sequentially arranged. For example, when the aliquots of N aresequentially arranged, one medium value or two median values may bedetermined as the number of subgroups.

When the resonators are grouped into subgroups as described above, it ispossible to reduce coupling between the resonators, and if necessary, itis possible to drive only some subgroups. Since the frequency bandranges covered by the respective subgroups are similar to one another,it is possible to achieve power-saving driving by driving only somesubgroups, although a resolution is slightly sacrificed.

FIG. 10 illustrates an example in which a plurality of resonators R_(k)are divided into m subgroups that are arranged in a circular shape, andFIG. 11 illustrates an example in which resonators are arranged in eachsubgroup of FIG. 10.

The plurality of subgroups SG_j (where j is a natural number from 1 tom) includes a group of resonators R_(k) having the same remainder whenthe index k naming the resonators R_(k) is divided by m. The pluralityof subgroups SG_j may occupy a fan-shaped area and be sequentiallyarranged along a circumferential direction.

In each subgroup SG_j, the resonators R_(k) are arranged along thecircumferential direction in order of the center frequencies. Theresonators R_(k) in each subgroup SG_j satisfy k=i*m+j (where i is aninteger from 0 to (N/m)−1). A frequency distance between two resonatorsspatially adjacent to each other, that is, two resonators (e.g., R₂ andR_(m+2)), of which an angular distance is 2π/N radians, is m*Δf. Δf is afrequency distance value determined according to a method of setting thecenter frequencies of the resonators R_(k). As described above, Δfcorresponds to a common distance when the resonators R_(k) are arrangedat equal-difference intervals, and corresponds to a common ratio whenthe resonators R_(k) are arranged at equal-ratio intervals. A physicaldistance between two resonators, of which the center frequencies areadjacent to each other, that is, two resonators (e.g., R₁ and R₂, orR_(m+1) and R_(m+2)) having a center frequency distance of Δf, is anangular distance of 2π/m radians.

FIG. 12 is a perspective view illustrating a schematic configuration ofa spectrum analyzer 200 according to another exemplary embodiment.

The spectrum analyzer 200 includes a support substrate 210 with athrough-hole TH, and a resonator array 220. The resonator array 220includes four subgroups SG_1, SG_2, SG_3, and SG_4 arranged according tothe above-described arranging method. An arrangement trajectory offixing portions of the resonators R has a circular shape.

FIG. 13 is a graph showing frequency response characteristics due tothree resonators arranged spatially adjacent to one another in thespectrum analyzer 200 of FIG. 12.

Resonators R₁, R₅, and R₉ belong to the same subgroup SG_1 and a centerfrequency distance between adjacent subgroups (e.g., SG_1 and SG_2) is4Δf. Although the resonators R₁, R₅, and R₉ are arranged most adjacentto each other, coupling occurs very weakly because the center frequencydistance is secured.

FIG. 14 is a graph showing frequency response characteristics due tothree resonators, whose center frequencies are close to one another, inthe spectrum analyzer 200 of FIG. 12.

Resonators R₁, R₂, and R₃ respectively belong to subgroups SG_1, SG_2,and subgroup SG_3 and have an angular distance of 2π/4 radians. Althoughthe center frequency distance is Δf, that is, the center frequencydistance is most adjacent, coupling does not almost occur because thespatial separation distance is secured.

FIG. 15 illustrates an example in which a plurality of resonators R_(k)are divided into m subgroups SG_j (where j is a natural number from 1 tom) arranged in a rectangular shape in a spectrum analyzer 300 accordingto another exemplary embodiment, and FIG. 16 illustrates an example inwhich the resonators R_(k) are arranged in order of center frequenciesin each subgroup SG_j of FIG. 15. N denotes the total number of theplurality of resonators R_(k).

The number m of subgroups SG_j may be set to be even number. Thesubgroups SG_1 to SG_m/2 are sequentially arranged vertically along oneside of the rectangular shape, and the subgroups SG_(m/2)+1 to m aresequentially arranged vertically along the other side of the rectangularshape.

This arrangement may be applied to the support substrate with arectangular through-hole. That is, fixing portions of the plurality ofresonators may be arranged along two parallel sides of the rectangularshape. In other words, an arrangement trajectory of the fixing portionsof the resonators belonging to the subgroups SG_1 to SG_m/2 may have ashape of a first straight line, and an arrangement trajectory of thefixing portions of the resonators belonging to the subgroups SG_(m/2)+1to SG_m may have a shape of a second straight line parallel to the firststraight line.

The resonators R_(k) in each subgroup SG_j satisfy k=i*m+j (where i isan integer from 0 to (N/m)−1). In each subgroup SG_j, the resonatorsR_(k) are arranged in order of the k values, and the resonatorsbelonging to different subgroups and facing one another have the samemagnitude order in the corresponding subgroups. For example, theresonators R₁ and R_((m/2)+1) face each other, and the resonatorsR_(m+1) and R_((3m/2)+1) face each other. As illustrated in FIG. 16, theshortest separation distance among the separation distances between theresonators belonging to different subgroups and facing one another isS1. A horizontal length A of the rectangular shape may be set based onthe S1 value.

FIG. 17 illustrates arrangement of resonators used in a spectrumanalyzer 400 according to a modification of FIG. 16.

Subgroups SG_j of the spectrum analyzer 400 are arranged in the samemanner as those of the spectrum analyzers 300 of FIGS. 15 and 16.However, the order of center frequencies of the resonators of thesubgroups SG_j facing one another is opposite to that in FIG. 16.

The resonators R_(k) in each subgroup SG_j satisfy k=i*m+j (where i isan integer from 0 to (N/m)−1). The resonators Rx in the subgroups SG_1to SG_m/2 are arranged in ascending order of the k values, and theresonators R_(k) in the subgroups SG_(m/2)+1 to m are arranged indescending order of the k values. That is, the resonator R₁ having thesmallest k value in the subgroup SG_1 faces the resonator R_((N+m)/2+1)having the largest k value in the subgroup SG_(m/2)+1.

Due to such an arrangement, an area occupied by the resonators R_(k) maybe further reduced than that in the case of FIG. 16, therebyimplementing a more compact structure. The shortest separation distanceamong the separation distances between the resonators belonging todifferent subgroups and facing one another is S2. When the horizontallength of the rectangular shape is A as in the case of FIG. 16, S2 isgreater than S1 illustrated in FIG. 16.

Therefore, in other words, when S2 is set to be S1 as in the case ofFIG. 16, a total length of the resonators R₁ and R_((N+m)/2+1) facingeach other is less than a total length of the resonators R₁ andR_((m/2)+1) facing each other in FIG. 16. Thus, the horizontal length Aof the rectangular shape for the arrangement of the resonators R_(k) maybe set to be less than that in the case of FIG. 16.

FIG. 18 is a perspective view illustrating a schematic configuration ofa spectrum analyzer 500 according to another exemplary embodiment.

The spectrum analyzer 500 includes a support substrate 510 with arectangular through-hole TH, and a resonator array 520. The resonatorarray 520 includes two subgroups SG_1 and SG_2. An area occupied by theplurality of resonators R may be minimized by reversing the centerfrequency order of the resonators of the subgroups SG_1 and SG_2 facingeach other.

FIG. 19 is a graph showing frequency response characteristics due tothree resonators R₁, R₃, and R₅ arranged spatially adjacent to oneanother in the spectrum analyzer 500 of FIG. 18.

The resonators R₁, R₃, and R₅ belong to the same subgroup SG_1 and acenter frequency distance thereof is 2Δf. Although the resonators R₁,R₅, and R₉ are arranged most adjacent to each other, coupling occursvery weakly because the center frequency distance is secured.

FIG. 20 is a graph showing frequency response characteristics due to tworesonators, whose center frequencies are adjacent to each other, in thespectrum analyzer 500 of FIG. 18.

The resonators R₃ and R₄ belong to subgroups SG_1. Although SG_2 and thecenter frequency distance thereof is Δf, that is, the center frequencydistance is most adjacent, coupling barely occurs because the spatialseparation distance is secured.

FIG. 21 is a plan view illustrating an example of a resonatorarrangement in a spectrum analyzer 600 according to another exemplaryembodiment.

Resonators R included in the spectrum analyzer 600 are arranged in foursubgroups in four regions defined by dividing a square region by twodiagonal lines. The resonators R having different lengths may besequentially arranged in the four regions in a triangular shape.

As illustrated in FIG. 18, the resonators R may be arranged on a supportsubstrate with a rectangular through-hole. However, exemplaryembodiments are not limited thereto. For example, the resonators R maybe arranged so that fixing portions are fixed on a beam structure havinga shape of two diagonal lines.

FIG. 22 is a plan view illustrating an example of a resonatorarrangement in a spectrum analyzer 700 according to another exemplaryembodiment.

Resonators R included in the spectrum analyzer 700 are arranged into msubgroups and are arranged in a polygonal region having m sides. Thesubgroups are allocated in m regions partitioned by diagonal lines, andresonators having different lengths are sequentially arranged in thesubgroups. A case where m is 8 is illustrated in FIG. 22, but this ismerely an example and embodiments are not limited thereto.

The resonators R may be arranged on a substrate having an m-polygonalthrough-hole. However, exemplary embodiments are not limited thereto.The resonators R may be arranged in a beam structure having a shapecorresponding to diagonal lines of an m-polygon.

FIGS. 23A to 23C are graphs showing examples of methods of settingcenter frequencies of resonators used in spectrum analyzers according toexemplary embodiments.

FIG. 23A illustrates an example in which a frequency range to beanalyzed is divided by equal-difference intervals. Values divided by theequal-difference intervals are assigned as center frequency valuestogether with identifications (IDs) of a plurality of resonators, andthe plurality of resonators are grouped into four subgroups according tothe given IDs by the above-described method.

FIG. 23B illustrates an example in which a frequency range to beanalyzed is divided by equal-ratio intervals. Frequency values set bythe equal-ratio intervals are assigned as center frequency valuestogether with IDs of a plurality of resonators, and the plurality ofresonators are grouped into four subgroups according to the given IDs bythe above-described method.

FIG. 23C illustrates an example in which a frequency range to beanalyzed is divided by arbitrary intervals. The arbitrary intervals maybe variously set as a mixture of equal-difference intervals havingdifferent common difference values, a mixture of equal-ratio intervalshaving different common ratio values, or a combination of theequal-difference interval and the equal-ratio interval. The setfrequency values are assigned as center frequency values together withIDs of a plurality of resonators, and the plurality of resonators aregrouped into four subgroups according to the given IDs by theabove-described method.

FIGS. 23A to 23C illustrate the method of setting the center frequenciesby dividing the frequency band into the four subgroups, but exemplaryembodiments are not limited thereto. It is possible to divide thefrequency band into various numbers of subgroups, and the method ofsetting the center frequencies may be modified by combinations of theabove-described methods or other forms.

The resonators having the movable portions driven by a cantilever methodhave been described above, but exemplary embodiments are not limitedthereto. The resonator arrangement methods described above may beapplied to various resonators showing a coupling phenomenon due to afrequency-adjacent or space-adjacent structure.

In the spectrum analyzers according to exemplary embodiments,frequencies of a certain band may be selectively sensed by a pluralityof resonators having different center frequencies, thereby facilitatingfrequency information analysis with respect to an input signal.

The spectrum analyzers according to exemplary embodiments need notperform a Fourier transform and may independently improve a frequencyresolution and a time resolution.

According to the method of arranging the resonators of the spectrumanalyzer, the coupling phenomenon between the resonators may be reducedby securing the spatial separation distance between the resonatorshaving adjacent center frequencies and/or the center frequency distancebetween the spatially adjacent resonators.

When the resonators are arranged based on the subgrouping methodaccording to the method of arranging the resonators of the spectrumanalyzer, coupling between the adjacent resonators may be reduced,thereby improving spectrum analysis accuracy. Also, if necessary, onlysome subgroups may be selectively driven, thereby achieving a reductionin power consumption.

The foregoing exemplary embodiments are merely exemplary and are not tobe construed as limiting. The present teaching can be readily applied toother types of apparatuses. Also, the description of the exemplaryembodiments is intended to be illustrative, and not to limit the scopeof the claims, and many alternatives, modifications, and variations willbe apparent to those skilled in the art.

What is claimed is:
 1. A spectrum analyzer comprising: a supportsubstrate; and a plurality of resonators that have center frequenciesdifferent from each other, one end of each of the plurality ofresonators being fixed to the support substrate.
 2. The spectrumanalyzer of claim 1, wherein each of the plurality of resonatorscomprises: a fixing portion fixed to the support substrate; a movableportion movable in response to an audio signal; and a sensor configuredto sense a movement of the movable portion.
 3. The spectrum analyzer ofclaim 2, wherein the support substrate comprises a through-hole, and themovable portion of each of the plurality of resonators faces thethrough-hole.
 4. The spectrum analyzer of claim 3, wherein the pluralityof resonators are arranged in a flat formation without overlapping oneanother.
 5. The spectrum analyzer of claim 4, wherein the fixingportions of the plurality of resonators are arranged to have atrajectory along a cross-sectional shape of the through-hole.
 6. Thespectrum analyzer of claim 4, wherein a cross-sectional shape of thethrough-hole is a rectangular shape, and the fixing portions of theplurality of resonators are arranged to have a trajectory along twoparallel sides of the rectangular shape.
 7. The spectrum analyzer ofclaim 1, wherein a separation distance between two resonators havingcenter frequencies immediately adjacent to each other, among theplurality of resonators, is greater than a shortest separation distanceamong separation distances between the plurality of resonators.
 8. Thespectrum analyzer of claim 1, wherein a center frequency differencebetween two resonators spatially immediately adjacent to each other,among the plurality of resonators, is greater than a smallest centerfrequency difference among center frequency differences between theplurality of resonators.
 9. The spectrum analyzer of claim 2, wherein,when N denotes a number of the plurality of resonators, R_(k) denotesthe plurality of resonators in order of center frequencies, k denotes anatural number from 1 to N, m is any one of aliquots of N other than 1and N, and j is a natural number from 1 to m, the plurality ofresonators are grouped into m subgroups SG_j, when j is different fromm, each of the subgroups SG_j includes resonators R_(k) satisfying (kmod m)=j, when j is equal to m, each of the subgroups SG_j includesresonators R_(k) satisfying (k mod m)=0, and resonators R_(k) belongingto a same subgroup SG_j are arranged adjacent to each other in order ofthe center frequencies.
 10. The spectrum analyzer of claim 9, whereinthe subgroups SG_j are arranged in order of the j values.
 11. Thespectrum analyzer of claim 9, wherein, m is one medium value or twomedian values of the aliquots of N.
 12. The spectrum analyzer of claim9, wherein m is a natural number greater than 2, and the fixing portionsof the plurality of resonators are arranged to have a trajectory in apolygonal shape, a circular shape, or a closed curve shape.
 13. Thespectrum analyzer of claim 10, wherein the fixing portions of theplurality of resonators are arranged to have a trajectory in anm-polygonal shape with m sides.
 14. The spectrum analyzer of claim 9,wherein m is an even number, and the fixing portions of the plurality ofresonators are arranged to have a trajectory in a shape of two straightlines parallel to each other.
 15. The spectrum analyzer of claim 14,wherein the fixing portions of the resonators belonging to subgroupsSG_1 to SG_m/2 among the subgroups SG_j are arranged to have atrajectory in a shape of a first straight line, and the fixing portionsof the resonators belonging to subgroups SG_(m/2)+1 to SG_m among thesubgroups SG_j are arranged to have a trajectory in a shape of a secondstraight line parallel to the first straight line.
 16. The spectrumanalyzer of claim 14, wherein resonators in a first subgroup of theplurality of resonators and resonators in a second subgroup of theplurality resonators face each other and are arranged in reverse orderof the center frequencies.
 17. The spectrum analyzer of claim 9, whereinwhen the center frequencies of the plurality of resonators are within arange between a first frequency F1 and a second frequency F2, the centerfrequencies of the plurality of resonators are F1+(k−1)(F2−F1)/(N−1),respectively, and wherein N is a number of the plurality of resonators,and k is a natural number from 1 to N.
 18. The spectrum analyzer ofclaim 9, wherein ratio of center frequencies of the two resonatorshaving center frequencies immediately adjacent to each other, among ofthe plurality of resonators, are set to have a constant value r.
 19. Amethod of arranging resonators of a spectrum analyzer, the methodcomprising: setting a frequency range of frequency f a number N of aplurality of resonators R_(k), when k is a natural number from 1 to N;setting center frequencies of the plurality of resonators R_(k) to bedifferent values within the set frequency range; setting an arrangementperiod p of the plurality of resonators R_(k); and arranging theplurality of resonators R_(k) so that a pitch between two resonators ofthe plurality of resonators R_(k), which have the center frequenciesimmediately adjacent to each other, is 2p or greater.
 20. The spectrumanalyzer of claim 19, wherein the frequency range is set to be betweenF1 and F2, the center frequencies of the plurality of resonators R_(k)are set to be F1+(k−1)(F2−F1)/(N−1), and the plurality of resonators arearranged so that a center frequency difference between two resonators ofthe plurality of resonators R_(k), which are spatially immediatelyadjacent to each other, is 2(F2−F1)/N or greater.
 21. The spectrumanalyzer of claim 19, wherein the center frequencies of the plurality ofresonators R_(k) are set at equal-ratio intervals r, and the pluralityof resonators R_(k) are arranged so that a center frequency ratiobetween two resonators of the plurality of resonators (R_(k)), which arespatially immediately adjacent to each other, is 2r or greater.
 22. Thespectrum analyzer of claim 19, wherein the plurality of resonators R_(k)are grouped into m subgroups SG_j when j is a natural number from 1 tom, and m is any one of aliquots of N other than 1 and N, when j isdifferent from m, each of the subgroups SG_j includes resonators R_(k)satisfying (k mod m)=j, when j is equal to m, each of the subgroups SG_jincludes resonators R_(k) satisfying (k mod m)=0, and resonators R_(k)belonging to a same subgroup SG_j are arranged adjacent to each other inorder of the center frequencies.
 23. A spectrum analyzer comprising: asupport substrate comprising a through-hole; and a plurality ofresonators, each of the plurality of resonators having a first end thatis fixed to the support substrate and a second end that extends from thefirst end toward the through-hole to be apart from the supportsubstrate, wherein the plurality of resonators are classified into mnumber of groups, m being a natural number, and wherein resonators in asame group among the m number of groups are disposed to be adjacent toeach other, wherein a difference between a central frequency of a firstresonator in one group and a central frequency of a second resonator inthe one group is a multiplication of m and Δf, wherein the Δf is Fdivided by N when F is a frequency range in which each of the pluralityof resonators operates and N is a number of the plurality of resonators.